The present invention is generally related to the field of printers and, more particularly, is related to a printing apparatus having a servicing sled that is adaptively controlled.
Inkjet printers are often used to print documents and images on a print medium. The print medium can include various types of media, such as paper, photographic print media, labels and so forth.
A conventional inkjet printer includes a movable inkjet printhead mounted on a print cartridge. A carriage assembly moves the print cartridge, and inkjet printhead, laterally over the print medium in successive passes. The print medium is advanced in a direction perpendicular to the motion of the printhead by a drive assembly so that the printhead can progressively lay down ink droplets corresponding to the desired pattern being printed.
The printhead has an array of nozzles, which are typically grouped into pens. Each nozzle generates ink droplets as the printhead moves over the print medium to produce the desired pattern on the print medium. Typically, each nozzle is formed by a nozzle chamber, a firing mechanism, and an orifice, with the firing mechanism being located within the nozzle chamber. Each nozzle is supplied with ink from an ink supply reservoir, noting that different nozzles can be supplied with ink from different ink reservoirs for printing multiple colors or for printing on different types of media.
A trend in inkjet printer technology has been to periodically clean (or service) the printhead by wiping the printhead (and particularly the nozzle orifices) with one or more wipers. The wipers typically resemble rubber squeegee devices. Servicing the printhead in such a manner tends to improve print quality and lengthen the useful life of a print cartridge by removing aerosol deposits, excess ink, dust, minute pieces of paper debris and other contaminants from the printhead.
Typically, the wipers are mounted on a servicing sled that is moved with respect to the printhead by a drive assembly. The drive assembly is configured to drive the sled with a predetermined amount of force. In a conventional inkjet printer, this force is set to be large enough to move the sled when taking into account variability in printer components (i.e., differences in printer parts from printer to printer), aging of the printer components and so forth. As a result, the force applied to the servicing sled is often excessive. Excessive force can lead to increased noise production from the printer during printhead servicing. These sounds can include, for example, mechanical xe2x80x9cwhiningxe2x80x9d or xe2x80x9cstrainingxe2x80x9d (as the sled is intentionally stalled against mechanical stops) and xe2x80x9cclackingxe2x80x9d caused by the sled hitting the mechanical stops. The increased noise production can be unsettling to a user of the printer. In addition, the excessive force can unduly stress printer components and can lead to premature failure of printer components.
Another characteristic of conventional inkjet printer servicing sled control is that if the sled becomes unintentionally stalled (e.g., stuck under the printhead), all printer operation is ceased. This characteristic can make the printer unreliable and can leave a user of printer without the ability to print even though the printer is otherwise operational to image the desired print job.
Accordingly, there exists a need in the art to enhance the control over the servicing sled of an inkjet printer.
According to one aspect of the invention, a method of adaptively controlling an amount of force applied to a servicing sled used to clean an inkjet printhead. The method includes: (a) applying a run force associated with a stored force level to the servicing sled; (b) sensing a first unintentional stall of the servicing sled during application of the run force; (c) selecting a lowest test force from a plurality of test forces to be a current test force; (d) applying the current test force to the servicing sled; (e) upwardly incrementing the current test force if a second unintentional stall of the servicing sled is sensed during application of the current test force, otherwise storing an adapted force level indication associated with the current test force in place of the stored force level indication; and (f) repeating operations (d) and (e) if the current test force is less than a highest test force form the plurality of test forces, otherwise storing an adapted force level indication associated with the highest test force in place of the stored force level indication.
According to another aspect of the invention, an inkjet printer. The inkjet printer includes a printhead adapted to progressively deposit ink droplets on a print medium and a servicing sled having a wiper for removing contaminants from the printhead. A drive motor is coupled to the servicing sled with a sled drive linkage to move the servicing sled with respect to the printhead. A sensor is adapted to generate a signal indicative of distance traveled by the servicing sled. A control assembly is adapted to control the drive motor so as to vary mechanical force applied to the servicing sled. The control assembly is programmed to select a run force from a plurality of run forces with which to move the servicing sled during a printhead service by controlling the drive motor to apply a test force from a plurality of test forces to the servicing sled, each test force corresponding to one of the run forces, and by comparing a distance traveled by the servicing sled during application of the test force and a predetermined distance to determine if the test force is sufficient to actuate the servicing sled.